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Leaching of Radionuclides from a Cement Composite Incorporating Evaporator Concentrates Generated at a Pressurized Water Reactor Nuclear Power Plant

Hideo Matsuzuru, Noboru Moriyama

Nuclear Science and Engineering / Volume 80 / Number 1 / Pages 14-25

January 1982

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The leaching behavior of a cement composite incorporating evaporator concentrates produced at a pressurized water reactor nuclear power plant has been studied for safety assessment of the final disposal of waste solids. Leaching tests were carried out in accordance with the method recommended by the International Atomic Energy Agency. Amounts leached were measured as functions of the waste-cement weight ratio (Wa/C), temperature of leachant, and curing time of specimens. The solidification of wastes containing boric acid with cement-vermiculite mixture was much improved by the alkalinization of the waste up to pH 12. The fraction of 3H or 90Sr leached increases with increasing Wa/C and leachant temperature, and with decreasing curing time. The amount of either 137Cs, 60Co, or 144Ce leached does not depend much on Wa/C, but depends on the leachant temperature and curing time. The leaching fraction for these nuclides in de-ionized water as a leachant is higher than that in the synthetic seawater. The leachabilities of nuclides follow the order: 3H > 137Cs > 90Sr > 60Co > 144Ce. The relationship between the fraction leached and the ratio of surface area and volume of a specimen has been examined in order to estimate the amounts leached from specimens of various geometries. On the basis of the results obtained, estimations were made of the amounts leached from a 200-ℓ composite volume that is exposed to a water environment for extended periods.

 
 
 
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